Dry eye syndrome, one of the most common eye disorders, is usually caused by a reduction of the quantity of tears produced or a decrease in the quality of the tear film that lubricates the eyes. Symptoms include itching, burning, irritation, redness, excessive tearing, blurred vision that improves with blinking, and increased discomfort after reading or watching TV.
There is a correlation between aging and decreased production of eye oil (60% less at age 65 than at age 18). The oil deficiency affects the tear film. Without adequate oil to seal the watery layer, the tear film evaporates faster, leaving dry areas on the cornea. Hot, dry or windy climates, high altitudes, air conditioning, and cigarette smoke also cause dry eye.
A number of approaches exist for treating dry eye. For example, one can supplement the tear film with artificial tears. However, too many applications are often required over the course of the day.
An aspect of this invention relates to an aqueous ophthalmic solution containing 0.2 to 2.5 (e.g., 0.5 to 0.8) percent by weight a polymeric demulcent, 0.045 to 0.065 (e.g., 0.05 to 0.06) percent by weight a calcium salt, and 0.14 to 1.4 (e.g., 0.3 to 1.2) percent by weight a phosphate salt. The ophthalmic solution has a viscosity of 20 to 150 (e.g., 50 to 90) centipoise and is buffered to a pH 5.5 to 8.5 (e.g., 6 to 8) with a phosphate salt or other suitable salts. It may further contain one or more of the following ingredients: 0.5 to 1.0 percent by weight glycerol, 0.5 to 1.0 percent by weight propyleneglycerol, 005 to 0.05 percent by weight glycine, 0.006 to 0.08 percent by weight sodium borate, 0.025 to 0.10 percent by weight magnesium chloride, and 0.001 to 0.01 percent by weight zinc chloride.
An effective amount of the above-described ophthalmic solution can be used to treat dry eye syndrome, and can also be used to treat another eye disorder if it contains a drug for that disorder. xe2x80x9cAn effective amountxe2x80x9d is the amount which is required to confer remedial or therapeutic effect.
Another aspect of this invention relates to a method of preparing polymeric demulcent-containing ophthalmic compositions, including those described above and others. The method includes immersing a polymeric demulcent in water or in an aqueous solution containing one or more ingredients (e.g., calcium chloride), agitating the water or the aqueous solution at 25xc2x0 C., i.e., room temperature, to 45xc2x0 C. (e.g., 30xc2x0 C. to 45xc2x0 C.) until the polymeric demulcent is dissolved to form a polymeric demulcent-containing solution, and optionally adding one or more other ingredients to the polymeric demulcent-containing solution.
The ophthalmic solution of this invention, when applied to the ocular surface of a subject, unexpectedly stays longer with the eye and, more importantly prolongs the integrity of the tear film. The extraordinary efficacy of this solution is attributed to its unique composition and the unique method by which it is prepared.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.